1 Cup Water
1 Cup Rice
While the mushrooms and tomato are cooking, put a pot on the stove to boil, with the 1 cup of water. Once it hits a boil, throw in your rice, give it a stir with a fork, cover, and turn down the heat to medium low. After around 10 - 15 minutes, pour in your tomato juice, stir it again, and replace the cover. It should take about another 10 minutes or so for your rice to be done.
When your rice is done, stir in your mushroom and tomato mixture. And you're done!